Newer versions of GIMP allow you to rotate brushes using the "Angle" feature on the tool options menu. Unfortunately this feature was not yet implemented in the 2.6 version of the software. To achieve the same result in the older version, you have to make use of a custom script. These scripts are available free online and when added to GIMP allows you to rotate any brushes already installed. This is a time saver if you use GIMP to design business materials such as business cards, letterheads or company forms that require specific brush shapes in various orientations.